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Finding the Fourth Proportional to 21.28, 31.75 and 20.51

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Solution

The fourth proportional to 21.28, 31.75 and 20.51 is: 30.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.28 : 31.75 = 20.51 : x
  2. Step 2: Convert to fraction form
    21.28/31.75 = 20.51/x
  3. Step 3: Cross multiply
    21.28x = 31.75 × 20.51
  4. Step 4: Simplify right side
    21.28x = 651.14
  5. Step 5: Solve for x
    x = 651.14/21.28
  6. Step 6: Final answer
    x = 30.61

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.